1. Field of the Invention
The present invention relates to a cooling device of a power supply, more specifically, to a cooling device of a power supply formed with a plurality of electricity storage blocks.
2. Description of the Background Art
In recent years, attention has been given to a vehicle which runs with driving force from a motor, such as a hybrid vehicle, a fuel cell vehicle or an electric vehicle, as one of measures to protect the environment. On such vehicle, a battery storing power for supply to the motor is mounted. A battery pack, formed by connecting a plurality of cells in series to form a module and then connecting a plurality of modules in series, is used as the battery. Though a high voltage (several hundred volts) is required to drive the vehicle, a voltage per one cell is low (for example, about 1.2 volts). Therefore, a total number of series-connected cells forming the battery becomes large and thus a size of the battery is increased. Therefore, in a vehicle having severe limitation of a space for mounting, the modules (cells) forming the battery are sometimes divided into a plurality of battery blocks. Each of the battery blocks is mounted in a separate location of the vehicle. Respective battery blocks are connected in series to form the battery. On the other hand, since the battery produces heat due to charging and discharging of power, it must be cooled. Therefore, for the battery formed with a plurality of separately mounted battery blocks, cooling of each battery block is required.
Japanese Patent Laying-Open No. 2003-142167 publication discloses a cooling device of a battery pack system formed with a plurality of battery pack blocks (battery blocks). The cooling device described in Japanese Patent Laying-Open No. 2003-142167 publication includes a temperature detection unit and a cooling fan provided on each battery pack block, and a control unit controlling each cooling fan by selecting any one of a plurality of control maps and, when a difference in temperatures of an arbitrary battery pack block and another battery pack block becomes larger than a threshold value, changing the control map for the cooling fan of the battery pack block for controlling. When the temperature detected is higher than a minimum temperature by at least a predetermined value, the control map for the cooling fan of the battery pack block is changed to a control map having a higher cooling capability. A volume of air supplied from the cooling fan is set based on the detected temperature and the control map.
According to the cooling device described in this publication, the control map for the cooling fan of a high-temperature battery pack block can be changed to the control map having a higher cooling capability to increase the volume of air supplied from the cooling fan of the high-temperature battery pack block. With this, a difference in temperatures of battery pack blocks can be decreased to make degradation speeds uniform to prolong an overall life.
It is to be noted that, though the volume of air supplied from the cooling fan sometimes deviates from a set value due to an effect of a pressure loss or the like, there is no description in Japanese Patent Laying-Open No. 2003-142167 publication as to how to drive the cooling fan to attain the volume of air as it is set. Therefore, the difference in temperatures may not be decreased because the volume of air supplied from the cooling fan may be different from the set value.